Social networking websites provide a dynamic environment in which members can connect to and communicate with other members. These websites commonly may provide online mechanisms allowing members to interact within their preexisting social networks as well as create new social networks. Members may include any individual or other entity, such as an organization or business. Among other attributes, social networking websites allow members to effectively and efficiently communicate relevant information to their social networks. For example, a member may post personal information, job information, biographical information, and other personalized content to areas of the website dedicated to the member. Other members may access the posted content by browsing member profiles or performing dedicated searches.
One popular type of content posted to social networking websites is images. Members often post images to communicate personal information to their social networks. For example, posted images may depict family, friends, locations, items, and any other subject matter in which a member may have interest. Social networking websites usually encourage the posting of images because the sharing of personal information fosters communication among members, and thus helps to realize the potential of the websites.
Certain images may contain content in which social networking websites take special interest for myriad reasons. For example, a social networking website may seek to intervene when the same photo is repeatedly posted by different members in violation of the website's terms of use or other guidelines. As another example, a social networking website may seek to restrict the posting of an image known by the website to contain inappropriate content. To identify these kinds of objectionable images, images may be compared for similarity or identity with images known to be objectionable. When images similar to objectionable images are identified, social networking websites may take appropriate action on them. However, due to the large number of images maintained by social networking websites and the significant computational expense in performing image comparisons, social networking websites confront challenges in efficiently identifying similar images.